PURPOSE: To normally control a developer in each of developer through-holes by uniformizing vibration in the vicinity of all of the developer through-holes of a printing head.
CONSTITUTION: An ultrasonic vibration applying device applying ultrasonic vibration to a printing head 100 consists of an ultrasonic vibration generating source 70 and the ultrasonic vibration transmission plate 80 having the ultrasonic vibration generating source 70 fixed thereto and transmitting the ultrasonic vibration generated from the ultrasonic vibration generating source 70 to the printing head 100. The ultrasonic vibration transmission plate 80 has comb tooth-shaped projections 81 extending toward a matrix electrode part 40 and fixed to the printing head 100 at the tips thereof. When the wavelength of the ultrasonic vibration generated from the ultrasonic vibration generating source 70 to be transmitted to the ultrasonic vibration transmission plate 8 is set to λ1 and the thickness of the plate 80 is set to (t), the width W of each of the comb tooth-shaped projections 81 satisfies conditions of W< λ1/2 and W≥t.
KIMURA TAKAHIKO
FUJII JUNJI
